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Overclocking Your Sega Genesis/MegaDrive
Deven "Epicenter" Gallo writes "I've recently been working on a project to alleviate the slowdown inherent in older game systems. How you ask? By overclocking them! I've managed to perfect overclocking the Sega Genesis / MegaDrive. The processor (a Motorola 68000, running at a stock speed of 7.6 MHz) can be pushed to 16.0 MHz in my experience, and I am still working on higher. The machine doesn't overheat and is entirely stable at these higher speeds."
... as the time I slapped a Type-R sticker on my Casio FX-1000 solar-powered calculator. Before I did that, it took 950 milliseconds to calculate 69! Afterward, it calculated 69! in 940 milliseconds flat.
Or, wait, maybe it was because the sun came out.
If you can overclock it so much with a noticeable performance, then why didn't Sega set it like that already, if it's so stable? Certainly it would have given them an edge...
Pushing a 7.6 --> 16MHz is over 100% more than the original! I have yet to see most people get anywhere near that on normal processors.
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Never criticize religion on Slashdot. You will be modded down for "Troll" no matter how factual it is.
I don't recall exactly, but I think you could 'overclock' the genesis in older emulators like Genecyst, so perhaps that would be a good way to check to see how well games run overclocked before you actually futz with your real Genny. I would think that many games would have timing problems at a speed greater than stock, particularly those that use raster effects. I can't say for certain, but I know my old Gameboy Color raster effects would break completely if I overclocked them. I would wager that racing games would probably suffer the worst.
for those of you who don't know, 'genesis' is the north american term whilst 'mega drive' is the UK (and european?) term
here are the specs and some history
Marge, get me your address book, 4 beers, and my conversation hat.
16mhz is what the Palm Zire runs at too. That means if someone ports Palm OS 4.1 and you attach a VGA/LCD thingy you can have a Sega brand PDA. True, you are sacrificing portability, but hey, I think there are some kids at my school with pockets big enough for a Genesis.
You'd think it would be most, but that doesn't appear to be the case:
I've written my own Nintendo Emulator. Just modified it to execute 5000 CPU instructions per scanline instead of the typical 114. Fired up Super Mario Brothers, Contra, and a few other games and they all appear to work fine.
I suspect (and I would've thought otherwise before this test) that many games are sychronized with the v blank interval or interrupts. I haven't tested sound, however, since I haven't written that part of the emulator yet.
get nemulator
Slowdown is an integral part of older consoles. Modern day emulators that can easily push these consoles with no slowdown at 60FPS impliment a technique to fake "slowdown." It's a lot easier to just grab a genesis emulator for your Dreamcast or Xbox than attempt a hardware mod like this.
"That may be justification alone for why the systems were underclocked at the factory. The clock in many games is based not on an actual clock but the speed of the processor... speed things up and you speed everything in the game up, and that's not very playable."
You're right. Even on newer consoles, like the Xbox, a 1.4 ghz cpu and 128 mb ram upgrade tends to have problems in certain games. Most console games, unlike their PC counterparts, run proportional to the CPU clock for actual game speed.
In a PC, overclocking the CPU will usually increase frame rate in newer games. Consoles, with their unified architecture, begin to run into compatibility problems when you make certain components run faster, or will usually speed up gameplay proportionally to the clock speed increase.
Yes, the above applies to the PC-like xbox too, but not to every game. From what I've been told, running Halo co-op splitscreen on that 1.4ghz xbox runs as smooth as silk.
Sigs are for losers
The center of your mindset should rest on the vertical blank - that's your 'unit of time', unless you're doing some splitscreen stuff (like the water effect in Sonic), then you utilize the horizontal IRQ (I also call it a line IRQ) to get there. No busywaiting necessary. Frame rate is mostly constant on the classic consoles, in the sense that it's mostly synched with the refresh rate.
FC Closer
His site explains that the games don't, in fact, run faster. Most Genesis games must actually be based on a clock instead of the processor speed. The only effect of the overclocking is that slowdown is eliminated. Don't you remember in Sonic games how if you had more than 20 or so rings and you got hit, the Genesis would slow to a crawl as it drew all the rings bouncing around on the screen? In two-player mode slowdown was even more common. Well if you overclock your Genesis, that can apparently be fixed.
main(c,r){for(r=32;r;) printf(++c>31?c=!r--,"\n":c<r?" ":~c&r?" `":" #");}
I am glad to see this as a root post. Anyone who has ever dug into the internals of the Amiga, Mac, or Atari ST hardware has found that moving to faster 680x0 CPUs did not affect game speed, only the amount of lag (we called it "bog") in a game.
;) Hell, we might still be able to see that just for kicks.
I have nearly two decades of experience with the 680x0 CPUs in the Amiga systems. I remember being absolutely thrilled when Sega used the 68000 CPU in the Genesis. I hacked an original unit which had the 68-pin package with a 68010. Honestly, I do not remember the full results, but I recall I was still able to play the majority of my collection (two carts at the time, hahahaha.)
I also toyed with the idea to replace the 68000 with an MTec 68020 accelerator pulled from my Amiga 500. I never tried it, and I still am not so sure it would have worked anyway. If the AmigaOS was a little less hard-wired to the Amiga hardware architecture, given a little work, we might could have seen AmigaOS running on a Genny
Having gone from 68000 to 68040 in all its discernable steps (I still dream of a 68060/PPC accelerator for my A4000,) I have been able to bring all of my games with me. The only problem I have is with expected timing of the OCS chipset versus the AGA chipset. But there are a number of great hard drive installers which over come this, as well as system "degraders" which place the computer in a state almost identical to the original Amiga hardware.
In any case, I'm inspired by this article and look forward to dropping a 12MHz clock generator in my Sega II (provided its CPU will support it.)
(climbing up on soap box) It is also worth mentioning that us old-hat gamers take a lot of shit for being so nostalgic and blah blah blah, aching for an era long-past. I got news for those who cast stones, many of those games were FUN, and down-right phuqn great. I will not say that none of my collections are nostalgic -- I have a number of Atari 2600 carts which I never played then and do not play now other than for testing, simply because they are Atari. But the majority of the games I collect (Amiga, Atari, Sega, NES, TI, C64, and others) WERE fun, and are STILL FUN.
How many people are still playing a "dead" console because the games rocked and you cannot get them for "modern" consoles? PS1 is almost 10 years old, and yet it still has a large following. I bet in 10 years there will still be a large faction of people playing the original XBox because some of the titles will not be available on newer consoles, or just will not play the same. (I do wonder how game play of XBox 1 games will be on the XBox 2...)
Well, enough of that.
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